The music score clearly specifies the length of all notes. So once you know how long a quarter note should last, for example, you already know the tempo and timing of entire score.

So why would you need to specify meter? I understand that the part of meter specifies the length of a note in terms of number of beats but I don't understand why we also need to specify the other part for where to place the bar.

Does it really matter if I decide to place bars every 4 beats or 8 beats? Is it really only for emphasis? What if I don't want any emphasis for my composition?

I tried playing simple tunes in software by only changing its meter and did not hear any differences for same score but different meters.

Try thinking up a musical phrase and sing it to yourself. Sing it in the style of a marching band, or a waltzing princess, or a plaintive slave, or a fervent Methodist, or ... Each time you will feel the stress and meter of each bar come through, the precise rhythm of the marching feet, the romantic sway of the dance. That's what your software failed to replicate.
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dumbledadJun 28 '13 at 10:29

4 Answers
4

As you say, "only" for emphasis - but emphasis is hugely important. People like music to have a pulse.

A musician would play these two lines differently, and someone with a musical background would be able to tell the meter just by listening:

There is a lot of subtlety to phrasing, but in blunt terms:

They would play the first note of each bar slightly louder

They would take a slight pause at the end of each bar

A computer program designed to mimic a human player would also make those two lines sound different. The programs you tried, either don't attempt anything so ambitious, or you had options turned off.

Although formally, every quarter-note is the same length, in actual performance, some notes are "pushed" and come early, and others are "pulled", and come late. This happens with the meter - for example, the third beat of every bar might be pulled.

To a large extent, human players can't help adding "swing" or "groove" by pushing an pulling notes, so the style that's the biggest exception is early sequenced electronic music, and subsequent music influenced by it. It didn't take long for sequencer designers to add a "swing" slider.

Some composers have written music with no meter. This is known as "free time". Eric Satie's Gnossiennes are some examples.

That Satie piece comes out as closer to 6/8 time although it's written in '4'.Even he put emphasis on certain notes, which meant it could have been written slightly differently, to give a better clue to the reader.Without bars, it can be played in so many ways,maybe Satie didn't want to specify too closely; this is a good reason for having bars.
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TimJun 28 '13 at 7:58

The player and the computer should not play it as such. It should be a choice in the mind not on the paper. Latin players for example like to accentuate the ah more than the first beat. That doesn't mean they write in a shifted pattern.
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user1306Jul 3 '13 at 14:54

Apart from the great answers talking about phrasing and emphasis, another purely technical consideration is synchronization.

If you don't have bars, it's very difficult to get everyone in an ensemble to rehearse a specific passage or phrase together. You could add rehearsal letters to a free-time score, sure, but it's very easy to say "ok, let's try it again from bar 58."

You also need some kind of sync points with the more complex and faster meters.

If you can, take a listen to the fast passages of The Sorcerer's Apprentice (Dukas) for instance. You might imagine this is in 9/8 and beaten in three - but it's not. It's in a very fast 3/8 and beaten in one. Without meter and bars, you could never get everyone together - it would be chaos.

(The joke here is that he didn't use 9/8 because Disney was paying him by the bar ;-)

There are also cases where composers like to play with the emphasis. Alfred Reed, for example, likes to use 5/4 bars but alternate the emphasis: 2+3, 3+2, 2+3, 3+2. Again, bars here help to keep you aligned as you play. Some composers (no name occurs to me at the moment) also score in one time signature, but place accents so that the music sounds like it's in another (these really mess me up).

Hope that helped too :-)

Edit: Here are a few interesting usages of meter from "El Camino Real" (Reed).

Showing the emphasis split within a bar - the conductor will usually conduct here in three, with the downbeats on the emphasis points.

Lazy meter changes - the double time signature here tells us that Reed's going alternate 4/4 with 3/4, and isn't going to write the changes in every time. This only lasts for 4 bars though.

Meter change with emphasis - this section, which is a rather slow fandango, Reed starts out in 5/8 (emphasis 3+2), but as the fandango section gets going, goes into 8/8 beaten in 3: 3+2+3 per bar. Notice that in these long bars there are no accents written. The emphasis guide tells you how to stress the first note of each group.

Most music naturally falls into rhythms. It's what makes music work in most cases. If one is trying to dance to it, it needs to be in rhythm.All the time signature (meter?) is there for is to tell the player/reader what to expect, without having to check out any further. 4/4 is so common, it's often stated with a 'C': when I write out music,in 4/4, I don't put time sig., as it's the default time.Thus, I only put numbers when it's NOT 4/4.
If it is not stated, looking at the bars may not help to anticipate the 'feel'. 3/4 has, for example, 6 quavers (8th notes) per bar, as does 6/8. But the feel of each is very different.Think 'Silent Night' - 3/4 or 6/8, or - does it matter? O.K., convention says they should be grouped differently, but to take your argument one step further.......
Yes, it's mainly for emphasis, initially at least, so the reader has a chance to recreate what the writer meant. Sometimes, when writing music, it's not easy to decide if it's 2 time or 4 time, but in deference to the guy who is going to read/translate it, a clue needs to be left.
When playing by yourself, maybe it matters less. In an ensemble situation(or a band/orchestra) it's very important, before everyone starts, that they all know the 'feel' of the piece. Yes, often, a tune is played 'cold' with NO rehearsal, and in these circumstances all clues are vital.

On a technical level you are right; note that the MIDI format has no meter but simply states "this note so loud so long" (the last one indirectly by a follow-up note-off event). The note representation is still clumsy in total however and so needs additional information in the form of text ("funeral march"), articulations, accents and so on. To reduce the amount of information to be applied to each note, a systematic pattern like a meter surely helps. Anybody who has struggled with a piece interchanging 3-beat and 4-beat passages is likely to confirm this. So there may be pieces, which don't benefit from a meter, but I'm not convinced there are many. I consider "only for emphasis" an understatement hardly to exceed, music lives from contrasts.